1.[ Strong Breaking Strength ] : zipline pulley has a maximum breaking strength of 30KN 6700LBS, so it can keep you in most outdoor applications, such as rescues, swing seats or backyard zipline settings, etc.2.[ Cable Diameter ] : This tandem speed dual trolley is specially designed for ropes and cables; Maximum rope diameter: 13mm/0.5in; Maximum cable diameter: 12mm/0.36in. Fits 1/4 5/16 3/8 1/2 inch cable or rope. This twin cart is extremely lightweight and durable enough for your outdoor adventures.3.[ Material ] : zip line pulley is made of aluminum and magnesium alloy shell and stainless steel pulley. The double sheaves of pulley provide great smooth rotation and efficient performance.4.[ Efficient Working ] : Two stainless steel discs with sealed stainless steel ball bearings prevent twisting for increased speed, efficiency and . Feature efficient bearings for high-speed adventure.This tandem pulley works better than a single pulley.